8.Suppose we wish to estimate the percentage of students who smoke cigarettes at each ofseveral colleges and universities. Two of the colleges are Wabash College (enrollment 900)and Purdue University (enrollment 36,000).What should the relative size of our samples befrom each school if we want the two sampling distributions to have approximately the samestandard deviation?
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9.In order to use the formula³´ˆ1pppnV±to calculate the standard deviation of the samplingdistribution of the sample proportion, which of the following conditions must be met?I.³´10 and110npnpt±II.The population’s distribution is approximately Normal.III. The sample size is less than 10% of the population size.t
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10.A census of the labor force in a large metropolitan area found that the time it takes for peopleto commute to work has a mean of 20.5 minutes and a standard deviation of 15.4 minutes.What is the probability that a random sample of 40 people have a mean commute time that isgreater than 25 minutes?§·¨¸±!¨¸¨¸¨¸©¹§·¨¸±!¨¸¨¸¨¸©¹§·¨¸±!¨¸¨¸¨¸©¹¹
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© 2011 BFW PublishersThe Practice of Statistics, 4/e- Chapter 7335